Such a video encoder is known from the patent application US2003/0031128. This document discloses a method for performing adaptive intra refresh (it is here recalled that the word “Intra” generally designates a mode according to which all the macroblocks of a frame are processed independently of any other frame, i.e. without any reference to another frame, whereas the word “inter” designates a mode according to which at least another frame is used as a reference, i.e. either a preceding frame, or a subsequent frame, or both). An intercede distortion value and an intracode distortion value are calculated as are an intercode bitrate and an intracode bitrate. Based on a comparison of the calculated intercode distortion value and the intracode distortion value, and on a comparison of the intercede bit rate and the intracode bit rate for each macroblock, a decision is made as to which predicted frame macroblocks are to be intracoded. According to this document, a distortion value is thus calculated from residuals but also from previous distortion data.
Such a method implies complex calculations of distortion like, for example, in equation 22 presented in this document. Such an approach is probabilistic and presupposes the use of a concealment step in the decoder in order to evaluate the impact of the encoding decision.